1. Field of the Invention
This invention relates to a content delivery service providing apparatus which performs the service of delivering content via a communication line to users' terminal units and to a user terminal unit which receives the service, and more particularly to the technique for protecting the copyright for content.
2. Description of the Related Art
With recent advances in communication techniques as found in the Internet, and in data compression techniques or the like in digital signal processing, a tremendous amount of content data, including music data, movies data, and game data, can be delivered, which enables users to receive content delivery services, regardless of time and place. Generically, a system to realize the content delivery service is such that a person who wants to buy or view (hereinafter, a user) accesses the content delivery center that is delivering the desired content, via the communication terminal unit, such as a personal computer or a set-top box (STB), informs a purchase or view request according the menu screen, and then is allowed to download or reproduce the content.
Presently, however, even if the user accesses the center, he or she can only get the introduction of content or the advertising content in the case of popular or topical content. Since most of the desired audio-visual full contents have to be bought by mail order, the user cannot view the content immediately. The reason is that the copyright owner of the content (or the copyright manager, hereinafter, both of the concepts are sometimes generically called the copyright owner) has not yet trusted the personal computer using a communication line, because of illegal copying. As described above, in spite of users' requests or business attractions, content delivery services are in a very passive situation in terms of the delivery of important content because of the illegal distribution problem.
On the other hand, some apartment house suppliers buy topical content from copyright owners to position themselves from the rest and offer services using a communication line to the customers in their own apartment buildings. In such a content distribution form, however, the following problems arise: a lot of content purchase money is needed and ordinary users cannot join the service.
Prior-art examples of a system related to the present invention include the following patent documents 1 to 5.
Patent document 1 (Jpn. Pat. Appln. KOKAI Publication No. 2001-344216) has disclosed a download system using a record-limit-information-added memory card. In the download system, the record limit information key and the content key are recorded as encrypted record limit information in a readable, writable protective area in the data area of a memory card after two-way authentication is successful, thereby preventing illegal download or making it impossible to rewrite or read easily the record limit information to charge for download, which enables content to be downloaded according to the record limit information.
Patent document 2 (Jpn. Pat. Appln. KOKAI Publication No. 2001-306954) has disclosed a data delivery system which acquires usage information from the unit in use each time delivery data is used and distributes the price for the data delivery to the related entities in the desired proportions on the basis of the usage information.
Patent document 3 (Jpn. Pat. Appln. KOKAI Publication No. 2000-349725) has disclosed a broadcast receiver unit which combines channel reception contract information with channel transmission contract information to form a usable contract information list corresponding to the specified content information, determines conditions for the use of content on the basis of the list, and controls the use of the reception content information on the basis of the conditions.
Patent document 4 (Jpn. Pat. Appln. KOKAI Publication No. 2000-339227) has disclosed a data operation method. In the data operation method, content is encrypted using the content key to create the encrypted content, a part of the content is extracted as sample data, watermark-included sample data in which the secret key obtained by encrypting the content key using the user information has been embedded as invisible information is created, and the combined data obtained by combining the watermark-included sample data with the encrypted content is delivered, thereby preventing not only the infringement of copyright but also the destruction or loss of permission information to decrypt the encrypted content.
Patent document 5 (Jpn. Pat. Appln. KOKAI Publication No. 09-134311) has disclosed a security system which writes the device ID, medium ID, permission information encrypted using the data encryption key, and encrypted data into a medium. When reading the data, the security system decrypts the data decryption key from the medium ID, permission information, and its device ID read from the medium, and decrypts the encrypted data read from the medium using the decrypted data decryption key, thereby enabling only the device with the device ID to make decryption and preventing the encrypted data from being decrypted even if the medium or recovery program is stolen, which maintains the confidentiality of the encrypted data on the medium.
Patent document 6 (Jpn. Pat. Appln. KOKAI Publication No. 2002-196982) has disclosed a system which includes a medium section where copyright-added content data is encrypted in a reproducible manner and recorded, and an information recording medium in which management information to determine whether to record or reproduce the copyright-added content data is recorded and which has a control unit with the function of authenticating each of a recording unit for performing a recording process and a reproducing unit for performing a reproducing process. Only when the authenticating function has authenticated the recording or reproducing unit and the management information has determined that recording/reproducing is possible, the system can record/reproduce the content data, thereby recording the content data, while protecting the data from illegal use.
As described above, in spite of users' requests or business attractions, content delivery services are in a very passive situation in terms of the delivery of important content, because the illegal distribution problem is an impediment to the trust of copyright owners.